1. Field of the Invention
The present invention relates to a self-developing camera with an improved processing liquid spreading device for processing a self-developing film unit.
2. Description of the Prior Art
A mono-sheet type of self-developing or instant film unit or otherwise called an integrated or non-peel apart type of self-developing or instant film unit (which is hereinafter referred to as an instant film unit for simplicity in the specification) and a variety of self-developing or instant cameras and printers for use with this type of instant film unit have been on the market. The mono-sheet type of instant film unit includes a transparent front cover sheet through which an exposure is made, a rear cover sheet disposed at the back of the front cover sheet, and a photosensitive and an image receiving layer formed between the front cover sheet and the rear cover sheet. The instant film unit further includes a pod containing a processing liquid therein which is placed at the leading end of the instant film unit and a trap operative to catch an excess of processing liquid therein which is placed at the trailing end of the instant film unit. The mono-sheet type of instant film unit is classified into two basic types, namely a reflective type and a transmissive type. In the reflective type, an latent image formed on the photosensitive layer is transferred as a positive image onto the image-receiving layer and after development the positive image is viewed from the side on which the exposure is made. In the transmissive type, on the contrary, a positive image formed on the image receiving layer after development is viewed through the transparent rear cover sheet. The mono-sheet type of instant film unit is otherwise classified into two types in terms of peripheral structures of the instant film unit, namely a spacer type of instant film unit and an outer-frame type of instant film unit. The spacer type of instant film unit has a spacer between the front cover sheet and the rear cover sheet along both sides of the film unit. The spacer has a thickness which governs a distributed thickness of processing liquid by the processing rollers while preventing the processing liquid from leaking or escaping out of the instant film unit during processing. The outer-frame type of instant film unit has a binder frame for binding around the periphery of the instant film unit to securely couple the front cover sheet and the rear cover sheet together so as to prevent the processing liquid from leaking out of the instant film unit during processing. A significant feature of the outer-frame type of instant film unit is that the difference with respect to the front cover or a space over the front cover which is provided by the outer binder frame cooperates with the processing rollers to govern a distributed thickness of processing liquid between a photosensitive and an image receiving layer during processing.
Such instant film units are used together with an instant camera or a printer in the form of a film pack. An instant film unit pack holds a number of instant film units received in a stack therein. The instant camera or the printer for use with the instant film unit is equipped with a processing liquid spreading device operative to spread a processing liquid between the front cover sheet and the rear cover sheet and, more specifically, between the photosensitive layer and the image-receiving layer. The processing liquid spreading device includes a pair of pressure-applying members, such as a pair of processing rollers, by which an exposed instant film unit is processed and advanced to come out of the instant camera or the printer. Some instant cameras have a spread controller which controls a uniform spread and distribution of the processing liquid by rubbing the surface of the instant film unit with pressure while the instant film unit is advanced.
However, in the instant camera equipped with the spread controller, a top of the spread controller projects beyond the natural path of the instant film unit which is directed to a contact line of the pair of processing rollers so as to force the instant film unit to advance in an S-shaped path with an effect of increasing the effect of spread controller. This structure causes from time to time the film unit at the leading end to fail to enter between the processing rollers, as a result of which the instant film unit is crimped or folded. Further ejection of the instant film unit by the processing rollers is completed by a specified time of rotation of a motor. If the instant film unit at its leading end abuts one of the processing rollers and is thereafter bit between and by the processing rollers, an error occurs between an advancing distance of a claw mechanism for advancing the instant film unit and an advanced distance by which the instant film unit is advanced forwarded by the claw mechanism, which results in causing the instant film unit to fail to be fully ejected out of the instant camera even after the processing roller have come to a full stop.
An object of the invention is to provide an instant camera which ejects an instant film unit out therefrom without crimping, folding or leaving it in the inside thereof while the spread control of processing liquid is made sufficiently to obtain a thin uniform distribution of processing liquid.
It is another object of the invention to provide an instant camera which gives a way that the instant film unit is reliably bit between a pair of processing rollers.
It is still another object of the invention to provide an improved processing liquid spreading device such as a pair of pressure-applying processing rollers particularly suitable for processing an outer-frame type film unit.
According to an embodiment of the invention, the instant camera is provided with a guide member which is disposed facing a spread controller in order to bring the leading end of an instant film unit into a bite of a pair of processing rollers by applying a processing pressure the instant film unit from one side opposite to the side of the instant film unit on which the spread controller rubs.
According to another embodiment of the invention, the processing liquid spreading device facing which an instant film unit egress slot of a film pack is located comprises a pair of pressure-applying processing rollers operative to rupture a pod containing a processing liquid therein and spread and distribute the processing liquid over a photosensitive layer while advancing the instant film unit, and a spread controller which is disposed between the instant film unit egress slot and the pressure-applying processing rollers and controls uniform distribution of the processing liquid between a front cover sheet and a rear cover sheet by giving the instant film unit an S-shaped film path. Either one of the pressure-applying processing rollers has smaller diameter portions at its both ends so as to apply a proper processing pressure on an exposed area of the instant film unit without causing a harmful influence on the uniform layer of processing liquid distribution due to a somewhat thick outer-frame of the instant film unit. The smaller diameter portion of the pressure-applying processing roller is divided into two sections adjacent to each other, namely a first small diameter section and a second small diameter section. The second smaller diameter section which is axially closer to the end of the pressure-applying processing roller is larger in diameter than the first smaller diameter section closer to the central portion of the pressure-applying processing roller. This roller configuration produces some gaps between the pair of pressure-applying processing rollers at their opposite end through which the instant film unit at the outer-framed opposite sides advances while it is processed.
Furthermore the spread controller is adjusted in its width so as not to contact the outer-frame to improve the spread control.